Method of internally coating rigid or semi-rigid plastic containers

ABSTRACT

A method for spin coating the interior of a generally rigid or semi-rigid plastic hollow article, such as a container or parison, with a synthetic organic resinous material to provide a protective coating therein. The method comprises placing a quantity of a dispersion of synthetic organic resinous material, preferably a latex or solution, in a hollow article, spinning the article at high speed thereby causing centrifugal force to distribute and hold a coating of the dispersion uniformly on the interior surfaces of the same and then heating the coating while continuing to spin the article. The result of the spin coating method is an article with a substantially uniform interior protective film providing improved article characteristics such as gas and liquid barrier properties, color and appearance, taste and flavor protection and the like.

United States Patent [191 Clark [451 Apr. 16, 1974 [75] Inventor: DaleE. Clark, Midland, Mich.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: May 26, 1971 [21] Appl. No.: 147,120

[52] US. Cl 117/101, 117/66, 117/95, .117/161 R, 117/161 UZ, 117/161 ZB,

[51] Int. Cl B44d 1/02 [58] Field of Search 117/95, 96, 101, 105.4,117/66,161ZB,162,161UZ,161R;

9/1969 Gilbert 264/94 12/1965 Smith ll7/96 X OTHER PUBLICATIONS Handbookof Material Trade Names, Zimmerman and Lavine (1953), pages 503 and 504.

Primary Examiner-Edward G. Whitby Attorney, Agent,or Firm-Arthur J.Young [5 7] ABSTRACT A method for spin coating the interior of agenerally rigid or semi-rigid plastic hollow article, such as acontainer or parison, with a synthetic organic resinous material toprovide a protective coating therein. The method comprises placing aquantity of a dispersion of synthetic organic resinous material,preferably a latex or solution, in a hollow article, spinning thearticle at high speed thereby causing centrifugal force to distributeand hold a coating of the dispersion uniformly on the interior surfacesof the same and then heating the coating while continuing to spin thearticle. The result of the spin coating method is an article with asubstantially uniform interior protective film providing improvedarticle characteristics such as gas and liquid barrier properties, colorand appearance, taste and flavor protection and the like.

18 Claims, 5 Drawing Figures FATENTEDAPR 16 197 v SHEEI 1 0F 2 o o IINVENTOR. 00/6 5. C /a/'k METHOD OF INTERNALLY COATING RIGID ORSEMI-RIGID PLASTIC CONTAINERS BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention relates to a method of coating hollowarticles, with particular reference to spin coating the interior ofplastic containers or parisons, for forming the same, with a dispersionof synthetic organic resin ous material which will enhance the end usecharacteristics of the containers or parisons.

2. Description of the Prior Art Coating the interior walls of acontainer with a protective film is well known. Generally the methodsused in the past to internally coat plastic, metal and paper containersare dipping, brushing or spraying. Also, in the metal can and papercontainer coating methods of the prior art, the coatings may be eithersprayed or brushed into the containers as they are rotated or placed inthe bottom of the containers and forced up the walls of the sameutilizing the centrifugal force generated by a subsequent rotationaloperation. The containers are then removed from the coating apparatusand dried in conventional hot air or infrared ovens.

One of the primary problems associated with the prior art coatingmethods, including spin coating, is their inability to form uniformcoatings without coating sag substantially in excess of 0.1 mil inthickness on the walls of a container without the addition of thickenerswhich are detrimental to the properties of the resulting film. Anotherproblem is their inability, when used to coat a latex, to completelywet-out and maintain a wetted surface of a nonporous substrate such as aplastic without the addition of substantial amounts of wetting agentswhich are also detrimental to the properties of the resulting film.

SUMMARY In general, the present invention provides a method foruniformly spin coating the interior walls of generally rigid orsemi-rigid plastic hollow articles such as a container or parison, forforming the same, with a synthetic organic resinous material,hereinafter commonly referred to as plastic material, which will resultin an article having an interior protective coating providing improvedcharacteristics. The method comprises placing, preferably spraying orbrushing, a quantity of a dispersion of plastic material in a hollowarticle, spinning the same at a high speed thereby causing centrifugalforce to distribute and/or hold a coating of the dispersion uniformly onthe interior wall surfaces of the article and then heating the coatingto dry or fuse the same while continuing to spin the article. Thedispersion of synthetic organic resinous material may be a latex,emulsion, suspension, solution or the like but is preferably a latex orsuspension. The article is spun at a high rate of speed of at least 100r.p.m., preferably from about 1,000 to 5,000 r.p.m., with the resultingcentrifugal force distributing and/or holding the dispersion uniformlyon the walls of the article. The coating may be dried or fused byinserting an infrared or other like heating element into the article,blowing hot air into.

the article, dielectric heating, microwave heating or other knownheating means or combinations thereof while continuing to spin the samewith the coating being held to the container walls by the centrifugalforce. The drying time of the coating is dependent on thickness ofcoating, amount and type of heating and the like. Application ofmultiple layers of coating, including adhesive or tie coatings appliedbefore the protective coatings, fall within the scope of the invention.

The plastic dispersion is preferably a latex or suspension of saran,polyvinyl chloride, polyamide, olefins, acrylonitrile, epoxy or otherlike plastic resins or copolymers or blends thereof which will form thedesired protective coating in the parison or container. The hollowarticles may be thermoformed by extrusion, injec tion molding, vacuumforming, blow molding and the like from polymers such as polystyrene,polypropylene, polyethylene, acrylonitrile butadiene styrene, styreneacrylonitrile, vinyl chloride, arylonitrile or like high structuralstrength polymers or copolymers or blends thereof which will not, inmost cases, meet the necessary requirements for the products containedtherein. The polymers in the article walls may be multiaxially molecularoriented or unoriented depending on desired end product. A more detaileddescription of various useful polymers will be discussed later.

The method described herein is directed towards, but not limited to, thefabrication of a pressurized or nonpressurized container for packagingfood products, oil and greases, beverages, medicine and the like wherethe protective coating helps provide improved container characteristicssuch as a barrier to oxygen, carbon dioxide, nitrogen, water or watervapor and organic vapor or liquid transmission into or out of thecontainer.

In addition to the above gas and liquid barrier properties, improvedcontainer characteristics such as color and appearance, taste and flavorprotection, stress crack and chemical resistance and the like may alsobe achieved. The method herein described provides many advantages overmore conventional prior art coating methods such as a symmetricallyuniform coating thickness without coating sag, improved adhesion of thecoating to the container or parison wall substrate due to forcedwetting, reduced need for wetting agents, thickeners or other additivesin the coating formulation, a more continuous layer of coating withsubstantially fewer pinholes therein due to a high degree of coalescenceof the wet coating during spinning of the container or parison and areduced drying time of the coating as, for example, where the polymer ina latex or suspension is of higher density than the suspending agents,such as a saran latex, the polymer is forced to the container or parisonwall leaving the suspending agent at the heated surface during spinningof the container where it can be more easily removed by drying.

As previously noted, the parisons coated by the method herein describedmay be used to form containers having an interior protective coating.Beneficially, coated containers can be formed from coated parisons byconventional blow molding. However, an additional advantage is obtainedby combining the spin coating method with a blow molding operation toform an internally coated container. By blow molding a containercontemporaneously with and immediately after the spin coating of aparison, the heat used to dry the coating can be also used to soften theinside parison walls prior to the actual blowing of the container. Theinterior heat in the spin coated parison need only be retained whileadditional external heat is applied to soften the parison before thecontainer blowing step. By using this sequence of steps, the timerequired to heat parisons for blow molding can be substantially reduced.

Accordingly, it is an object of the present invention to provide a newand improved method of coating the interior walls of rigid or semi-rigidplastic hollow articles such as parisons or containers. Another objectof the present invention is to provide a method of spin coating theinterior walls of hollow articles with a plastic material havingprotective properties. A further object of the present invention is toprovide a method for coating the interior walls of articles which willresult in a substantially uniform coating thickness without coating sag,improve adhesion of coatings to article wall substrates and provide amore continuous layer of coating with a substantially fewer number ofpinholes therethrough. A still further object of the present inventionis to provide a combined method for spin coating the interior ofparisons with protective coatings and then blow molding said coatedparisons into coated containers utilizing the heat for drying or fusingthe coatings in the parisons to help soften the parisons for subsequentblowing of the containers. Other objects of the present invention willbe apparent to those skilled in the art from the specification, drawingand claims.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiments of thepresent invention are shown in the accompanying drawings where:

FIG. 1 is an exaggerated cross-sectional view of a cup shaped containerfor food products and the like constructed according to the principlesof the present invention;

FIG. 2 is a side elevation view, with portions broken away, of a parisonwhich may be used to make a container and which is constructed accordingto the principles of the present invention;

FIG. 3 is a view like FIG. 1 only showing a modified bottle shapedcontainer;

FIG. 4 is a schematic representation of the sequence of steps followedin accordance with the principles of the present invention showing spincoating of a container similar to that shown in FIG. 1; and

FIG. 5 is a schematic representation of the sequence of steps followedin accordance with the principles of the present invention showing spincoating of a parison similar to that shown in FIG. 2 and then blowmolding of the same into an internally coated container utilizing theheat for drying or fusing the coating to help soften the parison priorto blowing the container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following descriptionillustrates the manner in which the principles of the invention areapplied but are not to be construed as limiting the scope of theinvention.

More specifically referring to FIGS. 1-3, plastic containers and 30 andparison illustrate the resulting interior coating obtained from the spincoating method herein described. Specifically, FIG. 1 illustrates aplastic cup-shaped container 10 having a side wall 12 and a bottom wall14. Container 10 is formed from a high structural strength thermoplasticmaterial 16. A plastic coating 18 is bonded to interior of walls 12 and14. FIG. 2 illustrates a parison 20 used to blow mold a container,similar to that shown in FIG. 3, having a thermoplastic wall 22 to whicha coating 24, similar to coating 18 shown in FIG. 1, is bonded. FIG. 3illustrates a bottle shaped container 30 having a side wall 32, a bottomwall 34 and a neck portion 36 which is formed from a thermoplasticmaterial 38. A coating 39, similar to coating 18 shown in FIG. 1, isbonded to the interior of walls 32 and 34 and the neck portion 36.

Referring now to FIGS. 4 and 5, the steps of the method utilized in thepresent invention are illustrated. Specifically in FIG. 4, step 1illustrates the selection of a container, similar to that shown in FIG.1, which is then spun and sprayed on the interior walls with a syntheticorganic resinous dispersion, as shown in step 2. Step 3 of FIG. 4illustrates the drying or fusion of the distributed coating while beingheld to the container walls by the centrifugal force with an infraredheating element which is inserted into the container while continuing tospin the same. Step 4 illustrates the resulting container with aninternal protective coating adhered to the walls of the container. Steps1 and 2 of FIG. 5 illustrate the selection and spin coating of aparison, similar to that shown in FIG. 2, following the same procedurerepresented by FIG. 4. In step 3, the parison is held by a heatedmandrel to retain the drying or fusion heat within the parison and isexternally heated in an oven utilizing any known heating means. Step 4of FIG. 5 illustrates the subsequent blow molding of the internallycoated parison and step 5 illustrates the resulting internally coatedblown container which is similar to the container shown in FIG. 3.

For a more complete understanding of the nature and scope of theinvention and to better demonstrate its advantages, reference may now behad to the following detailed examples thereof.

Example 1 To illustrate the method herein described, a plasticcup-shaped container, like container 10 shown in FIG. 1, having a wallthickness of about 50 mils, a diameter of about 3% inches and a heightof about 4 inches formed of a general purpose polystyrene material wasselected. A variable speed motor fitted with a spindle wihch holds thecontainer was used to spin the container. The container was placed inthe spindle and 3 grams of a saran latex poured into the same. Thecontainer was then spun for 10 seconds at about 5,000 rpm. with theexcess latex allowed to flow out the mouth of the container. Whilecontinuing to spin the container, a 600 watt infrared heating elementwas inserted into the container for 10 seconds to dry the latex. Thedried coating thickness was a uniform 0.4 mils on the side wall and 0.1mils on the bottom wall.

The saran latex used in this example was formulated with about 57 weightpercent solids and 2 weight percent wetting agent. The saran componentcomprises about weight percent of a copolymer of vinylidene chloridewith the balance being acrylonitrile and methyl methacrylate copolymers.The wetting agent is of the type generally referred to as analkylphenoxypoly(oxyethylene)ethanol having the general formula RC I-IO(CH CI-I O),,CH CH OH in which R may be C I-I or a higher homolog.

The coating on the container side wall demonstrates very good adhesionand could be removed with a 9% inch wide strip of No. 810 Scotch tapeonly after three attempts in the same area of the wall. The dried filmexhibited complete wet-out on the container walls.

For comparative purposes, a flat sheet of a similar general purposepolystyrene material was coated with the same saran latex using a wirewound rod and then dried for seconds with a 600 watt infrared heatingelement. The dried film exhibited incomplete wetting out on the flatsheet. A 0.4 mil thick portion of the coating was easily removed withtape from the sheet with only one attempt. The difference in adhesionand wet-out were attributed to the forced wetting of the walls of thecontainerwhen the spin coating method herein described was used.

Example 2 To demonstrate the uniformity and lack of coating sag achievedby the spin coating method, a cup-shaped container similar to thatdescribed in Example 1 was spin coated at 1,800 r.p.m. The same saranlatex and spinning and drying times were used. The resulting driedcoating on the interior side wall of the container was a uniform 0.4 milthick. Asecond container was spin coated following the same procedureexcept that the spinning step was discontinued before the coating wasdried with the infrared heating element. The resulting dried coating onthe side wall of the container exhibited severe coating sag andnonuniformity. Example 3 To demonstrate the improved barrier propertiesof a container coated with the method herein described, a cup-shapedcontainer, like container 10 in FIG. I, having a wall thickness of about40 mils, a diameter of about 3% inches and a height of about 3% inchesformed of a high density polyethylene material was selected. The sameprocedures and equipment used in Example 1 are employed here. Threegrams of a saran latex was placed in the container, the container wasspun at about 5,000 rpm. for 10 seconds and then dried for seconds whilecontinuing to spin the container.

The high density polyethylene forming the container walls waspolymerized by Ziegler catalysts and had a density of about 0.959, amelt index of about 0.5 and a flexual modulus of about 170,000. Thesaran latex used here was the same as that used in Example 1 except itwas formulated with about 4 weight percent wetting agent.

The resulting dried coating was a uniform 0.3 mil thick on the side wallof the container. The average oxygen transmission rate determined bymass spectrometer analysis of two samples taken from the side wall ofthe container was found to be 0.63 cubic centimeter per 100 squareinches per day at atmospheric pressure and 23C. The average oxygentransmission rate, tested in the same manner, of four 40 mil thicksamples taken from the side wall of a similar uncoated container wasfound to be 2.78 cubic centimeters per 100 square inches per day atatmospheric pressure and 23C. Example 4 To illustrate the method of spincoating and blow molding of a parison, like the parison with a taperedside wall shown in FIG. 5, into an internally coated container, likecontainer 30 of FIG. 3, an injection molded, closed end, multiaxiallyoriented, general purpose polystyrene parison was selected which had awall thickness of about 40 mils, a base diameter of 1% inches and anupper diameter just below the neck of 1% inches and an overall height of4% inches. The same procedures and equipment used in Example 1 areemployed here. Two grams of a saran latex was poured into the parison,

the parison was spun for 2 seconds at 5,000 rpm. and then a 500 wattinfrared heating element was inserted into the parison for 4 seconds todry the latex while continuing to spin the parison. A second coating ofthe latex was applied over the first coating using the same conditionsand procedures as described above. The dried coating had an evenlydistributed thickness of 0.4 mil at the bottom and 0.6 mil at the top ofthe parison with the average being 0.5 mil.

The saran latex used in this example was formulated with about weightpercent solids and 2 weight percent wetting agent. The saran componentcomprised about 92 weight percent of a copolymer of vinylidene chloridewith the balance being an acrylonitrile copolymer. The wetting agent wasthe same general type employed in Example 1.

The coated parison was then blow molded using conventional equipment. Toheat soften the parison, it was placed on a mandrel, similar to thatshown in FIG. 5, which had a surface, temperature of 220F. Externalheating was accomplished by placing the parison and mandrel for 14seconds in an oven heated by radiant heating elements having a surfacetemperature of l,000F. The parison was then placed in a mold and blowninto a container, like container 30 shown in FIG. 3, with an airpressure of psi. for a period of 5 seconds. The dwell time of thecontainer in the mold was 3 seconds. The blow molded container had anaverage side wall thickness of about 10 mils, a body diameter of 3 3/16inches, a neck diameter of 1 /8 inches and height of 4% inches. Thecoating on the side wall of the container was reduced in thicknessproportionally with the reduction in thickness of the side wallsubstrate and had an average thickness of about 0.125 mils.

Examination of the blown container showed that it exhibited thecharacteristic increased toughness of a multiaxially molecular orientedcontainer. Also, the coating had sufficient adhesion to the containerwall substrate to flow therewith without any detachment when thecontainer was blown. The coating in the blown container was continuousand pinhole free as determined by placing a mineral spirits and red dyesolution into coated and uncoated blown containers for a period ofone-half hour. The uncoated general purpose polystyrene containers werestained red whereas the coated containers remained unchanged. Theaverage oxygen transmission rate detennined by mass spectrometeranalysis of three samples taken from the side wall of the coatedcontainers was found to be 0.93 cubic centimeter per hundred squareinches per day at atmospheric pressure and 23C. The average oxygentransmission rate, tested in the same manner, of three samples takenfrom the side walls of similar uncoated containers is found to be 23.0cubic centimeters per hundred square inches per day at atmosphericpressure and 23C.

It is emphasized that a wide variety of materials may be employed incoating containers in accordance with the present invention.Particularly suited polymers are vinylidene chloride, vinyl chloride,acrylonitrile, vinylidene fluoride and/or combined mixtures thereof.Especially advantageous and beneficial are compositions of vinylidenechloride polymers, wherein the polymers contain at least about weightpercent vinylidene chloride, the remainder being one or moreolefinically unsaturated monomers copolymerizable therewith. Suitablevinylidene chloride polymers are prepared utilizing such comonomers asmethyl, ethyl, isobutyl, butyl, octyl and 2-ethylhexyl acrylates andmethacrylate; phenyl methacrylate, cyclohexyl methacrylate,pcyclohexylphenyl methacrylate, chloroethyl methacrylate,p-cyclohexylphenyl methacrylate, chloroethyl methacrylate,2-nitro-2-methylpropyl methaerylate, and the corresponding esters ofacrylic acid, methyl alphachloro-acrylate, octyl alphachloroacrylate,methyl isopropenyl ketone, acrylonitrile, methacrylonitrile, methylvinyl ketone, vinyl chloride, vinyl acetate, vinyl propionate, vinylchloroacetate, vinyl bromide, styrene, vinyl naphthalene, ethyl vinylether, N-vinyl phthalimide, N-vinyl succinamide, N-vinyl carbazole,isopropenyl acetate, acrylamide, methaerylamide or monoalkylsubstitution products thereof, phenyl vinyl ketone, diethyl fumarate,diethyl maleate, methylene diethyl malenate, diehlorovinylidenefluoride, dimethyl itaconate, diethyl itaconate, dibutyl itaconate,vinyl pyridine, maleic anhydride and allyl glycidyl ether. It is alsofrequently advantageous and beneficial to incorporate therein a minorportion of a plasticizer and a heat and/or light stabilizer. Othercompositions which may be used with benefit in coatings in accordancewith the present invention are vinyl chloride polymers which contain apredominant amount of vinyl chloride therein. Fluorocarbon polymers,fluorohydrocarbon polymers and fluorohalohydrocarbon polymers may alsobe used with benefit. Such materials as polyvinylidene fluoride,chlorinated polyethylene and polymers of such materials as vinylidenefluoride, vinylidene fluoride and chlorotrifluoroethylene,chlorotrifluoroethylene and vinylidene fluoride, chlorotriflu- It isconceivable that a variety of article configurations such as acup-shape, frustoconical shape, cylindrical shape and the like, whichare rotationally symmetrical and which have any desired wall thicknessand plastic composition, may be internally coated by the method hereindisclosed. Also, the dried interior coating thickness has a preferredrange of about 0.1 to 1.0 mils, but can be varied considerably bychanging the coating formulation and the spinning rate and time used.

Thus, while certain representative embodiments and details have beenshown for the purpose of illustrating the invention, it will be apparentto those skilled in the art that various changes and modifications canbe made therein without departing from the spirit and scope of theinvention.

What is claimed is:

l. A method for internally coating a generally rigid or semi-rigidplastic container or parison type hollow article comprising:

a. placing a quantity of a dispersion of synthetic organic resinousmaterial into said article;

b. spinning said article at a rate of speed sufficient to distribute andhold a coating of said dispersion uniformly on interior wall surfaces ofsaid article; and

c. heating said coating sufficient to dry or fuse the same whilecontinuing to spin said article.

2. The method of claim 1 wherein said article is formed of a polymerwhich is multiaxially molecular oriented.

3. The method of claim 1 wherein said article is a parison which is blowmolded into an internally coated container contemporaneously with andimmediately after said heating step 0 thereby utilizing said drying orfusion heat from step c to help soften said parison before blow moldingthe same.

4. The method of claim 3 wherein said blown container has a wallsubstrate polymer which is multiaxially molecular oriented.

5. The method of claim 1 wherein said dry coating has gas and liquidbarrier properties.

6. The method of claim 5 wherein said dispersion comprises a latex themajor resin component of which is a copolymer having copolymerizedtherein at least about weight percent vinylidene chloride and aremainder of one or more copolymerizable olefinically unsaturatedmonomers.

7. The method of claim 5 wherein said dispersion comprises a suspensionthe major resin component of which is a copolymer having copolymerizedtherein at least 70 weight percent vinylidene chloride and a remainderof one or more copolymerizable oleflnically unsaturated monomers.

8. The method of claim 5 wherein said dispersion comprises an emulsionthe major resin component of which is epoxy resin.

9. The method of claim 5 wherein said dispersion comprises a suspensionthe major resin component of which is epoxy resin.

10. The method of claim 5 wherein said dispersion comprises a latex themajor resin component of which is acrylonitrile polymer.

11. The method of claim 5 wherein said dispersion comprises a suspensionthe major resin component of which is acrylonitrile polymer.

12. The method of claim 1 wherein said heating of said coating isaccomplished by inserting an infrared heating element or other likeheating element into said article.

13. The method of claim 1 wherein said heating of said coating isaccomplished by blowing hot air into said article.

14. The method of claim 1 wherein said heating of said coating isaccomplished by dielectric heating.

15. The method of claim 1 wherein said heating of said coating isaccomplished by microwave heating.

16. The method of claim 1 wherein said dry coating has a range fromabout 0.1 mil to about 1.0 mils in thickness.

17. The method of claim 1 wherein said parison or container is spun at ahigh rate of speed of at least r.p.m.

18. The method of claim 1 wherein said placing said dispersion into saidarticle is accomplished by spraying.

2. The method of claim 1 wherein said article is formed of a polymerwhich is multiaxially molecular oriented.
 3. The method of claim 1wherein said article is a parison which is blow molded into aninternally coated container contemporaneously with and immediately aftersaid heating step c thereby utilizing said drying or fusion heat fromstep c to help soften said parison before blow molding the same.
 4. Themethod of claim 3 wherein said blown container has a wall substratepolymer which is multi-axially molecular oriented.
 5. The method ofclaim 1 wherein said dry coating has gas and liquid barrier properties.6. The method of claim 5 wherein said dispersion comprises a latex themajor resin component of which is a copolymer having copolymerizedtherein at least about 70 weight percent vinylidene chloride and aremainder of one or more copolymerizable olefinically unsaturatedmonomers.
 7. The method of claim 5 wherein said dispersion comprises asuspension the major resin component of which is a copolymer havingcopolymerized therein at least 70 weight percent vinylidene chloride anda remainder of one or more copolymerizable olefinically unsaturatedmonomers.
 8. The method of claim 5 wherein said dispersion comprises anemulsion the major resin component of which is epoxy resin.
 9. Themethod of claim 5 wherein said dispersion comprises a suspension themajor resin component of which is epoxy resin.
 10. The method of claim 5wherein said dispersion comprises a latex the major resin component ofwhich is acrylonitrile polymer.
 11. The method of claim 5 wherein saiddispersion comprises a suspension the major resin component of which isacrylonitrile polymer.
 12. The method of claim 1 wherein said heating ofsaid coating is accomplished by inserting an infrared heating element orother like heating element into said article.
 13. The method of claim 1wherein said heating of said coating is acComplished by blowing hot airinto said article.
 14. The method of claim 1 wherein said heating ofsaid coating is accomplished by dielectric heating.
 15. The method ofclaim 1 wherein said heating of said coating is accomplished bymicrowave heating.
 16. The method of claim 1 wherein said dry coatinghas a range from about 0.1 mil to about 1.0 mils in thickness.
 17. Themethod of claim 1 wherein said parison or container is spun at a highrate of speed of at least 100 r.p.m.
 18. The method of claim 1 whereinsaid placing said dispersion into said article is accomplished byspraying.